This book is written specifically for non-experts who want to gain a deeper understanding of language assessment and its role in real educational contexts. Although language assessment is often viewed as a specialized subfield of applied linguistics, it affects a broad network of stakeholders, including teachers, school administrators, parents, corporate trainers, and anyone involved in evaluating language performance. Recognizing that many practitioners must design tests or interpret student performance without formal training, the author aims to make language assessment concepts approachable, relevant, and easy to understand. The book synthesizes the author’s doctoral research and three major grant-funded projects supported by JSPS Kaken, all of which incorporated eye-tracking methods. These studies explored how learners process integrated tasks involving multiple texts and visual information, and they demonstrated how eye-tracking can reveal patterns of attention, cognitive behavior, and problem-solving strategies. By revisiting this body of research, the author offers both retrospective insights and forward-looking perspectives on the future of language assessment research.